4xcrazy
3/4 ton status
ESC module 3 times, 4th with a completely brand new (not reman'd) distributor.
believe me, there's spark.
believe me, there's spark.
CK5
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continued injector signal pulse failure issues
- Thread starter 4xcrazy
- Start date
As Russ said, if the ECM isn't SEEING the signal, it will stop firing the injectors, regardless if there is actually spark.
Here is a bit of chart you can follow http://www.73-87chevytrucks.com/techinfo/TroubleshootingTBISystems.pdf
I will always add that there may be wire troubles or connector troubles (even at the ECM) that the troubleshooting charts do NOT cover, so that sort of stuff must be checked before replacing parts.
Here is a bit of chart you can follow http://www.73-87chevytrucks.com/techinfo/TroubleshootingTBISystems.pdf
I will always add that there may be wire troubles or connector troubles (even at the ECM) that the troubleshooting charts do NOT cover, so that sort of stuff must be checked before replacing parts.
Ok, lets start from the very top in point form:
Ignition System:
1. Distributor = replaced with a quality new piece fitted with a good ignition module and a quality pickup coil.
2. ESC module = Replaced with the correct part number for your year and engine displacement. The knock sensor is verified as working correctly by observing a change in timing when a hammer is tapped on the side of the enigne or exhaust manifold.
3. Ignition coil = Solid, hot blue spark that does not cut out or fade to a fuzzy red spark as it warms up. Resistance is found to be within spec and it has a solid un-interrupted power supply and solid connections between it and the ignition module.
4. The spark plug wires are not shorting to ground or of high resistance from one end to the next.
5. Spark plugs are good and properly gapped.
6. The timing is set between 0 and 5 degrees DTDC (0 is the spec, I find most TBI engines don't mind a little bit extra down low than is programmed into the ECM and bump the baseline a bit, the ECM can't tell but will retard the timing if pinging is detected) with the set timing connector disconnected. The timing is observed to increase when the connector is re-connected.
Fuel System:
1. The fuel pump has been proven to be providing adequate FLOW in addition to generating pressure. Remove the return line at the tank and force the fuel pump to run. Lots of liquid returning to the tank? Pressure does not equal flow!
2. The fuel pressure regulator is maintaining a pressure of around 12 PSI of fuel pressure
3. The injectors are verified as having the correct part number as those called for in your year and displacement of engine.
4. You have verified a solid, uninterrupted power supply to each injector
5. You have verified the operation of the fuel pump via the oil pressure switch on the back of the intake (3 PSI or greater = fuel pump runs)
6. You have verified the operation of the fuel pump relay on the firewall and that it is receiving and sending an un-interrupted supply of power to the fuel pump for extended periods of time (hot coil = reduced magnetism = power off to the fuel pump if the oil pressure switch has failed)
Controls:
1. Spark plug wires are routed so they will not electrically interfere with the unsheilded signal wiring in the control harness.
2. The ECM is reciving an un-interrupted battery supply voltage on pins B1 and C16.
3. The ECM is recieving an ignition controlled voltage supply on pin A6 whenever the key is in the ON or CRANK positions
4. The ECM is securely grounded to the engine block on pins A12 and D1
5. The ECM is securely grounded to the engine block and has a solid ground connection to the O2 sensor on pin D6
6. The ECM is properly connected to the ignition module via the white wire from pin D4 on the ECM to terminal D on the ignition module (grounding this wire with the ignition on should activate the fuel pump relay) as well as the white / purple wire from pin B5 on the ECM to terminal C on the ignition module. This wire carries the reference pulses from the pickup coil
7. The ECM is properly connected to the ESC module with a yellow / red wire from pin B7 on the ECM to terminal C on the module. This wire sends an ignition retard signal to the ECM when pinging is detected.
Other checks:
1. You have properly set minimum air on the throttle body (short the ALDL port with the ignition on to display codes for 45 seconds, disconnect the IAC, start the engine and set the idle to approx 450 rpm, shut down, reconnected the IAC and remove the battery cables for 5 minutes to re-set the ECM and clear the IAC codes)
2. Your engine has no vaccum leaks in the throttle body shafts, intake gaskets, vaccum booster or other vaccum accessories. It maintains 18 - 20 inHG of vaccum at idle.
3. The EGR valve is in good operating condition and is the correct part for your intake manifold (the wrong valve may fit your intake, but cause a massive internal vaccum leak)
4. Your engine is equipped with a proper TBI camshaft. Camshafts used for even a stock carb engine will not function properly with a TBI engine unless programmed for it.
5. Your engine is equipped with stock TBI heads. Any other heads will require re-programming. TBI is a speed density system that operates on a large number of assumptions of flow values carefully mesured on the stock engine.
6. Your engine is not suffering any mechanical issues (valve timing due to sloppy timing chain, incorrect valve lash, low compression, incorrect combination of engine parts etc)
7. You have verified the operation of all the engine sensors and actuators. Make sure you have believeable CTS, TPS and MAP sensor readings as compared to actual atmospheric readings taken by other instruments.
If all of this stuff checks out, then I am going to state that your ECM has failed. If you've replaced it already and kept your memcal, then I would suspect a problem with the memcal. If your ECM and memcal test out good on another TBI truck, along with your modules, distributors etc then your problem must be wiring. If your grounds and power supplies are good, then it must lie in the signal wiring.
TBI is simple, incredibly robust and reliable. If you set it up for success, you'll have a life time of solid operation out of it. But if you slap a TBI on an old carb engine, or swap to an aftermarket cam shaft that isn't designed to run with a TBI engine you will have endless problems with it. Speed density is a very simplistic injection platform that operates on a lot of assumptions about the engine. It has no way of measuring the actual flow of air or compression in the cylinders etc so all the fuel and timing requirements are inferred. This is why TBI does not like engine mods.
Ignition System:
1. Distributor = replaced with a quality new piece fitted with a good ignition module and a quality pickup coil.
2. ESC module = Replaced with the correct part number for your year and engine displacement. The knock sensor is verified as working correctly by observing a change in timing when a hammer is tapped on the side of the enigne or exhaust manifold.
3. Ignition coil = Solid, hot blue spark that does not cut out or fade to a fuzzy red spark as it warms up. Resistance is found to be within spec and it has a solid un-interrupted power supply and solid connections between it and the ignition module.
4. The spark plug wires are not shorting to ground or of high resistance from one end to the next.
5. Spark plugs are good and properly gapped.
6. The timing is set between 0 and 5 degrees DTDC (0 is the spec, I find most TBI engines don't mind a little bit extra down low than is programmed into the ECM and bump the baseline a bit, the ECM can't tell but will retard the timing if pinging is detected) with the set timing connector disconnected. The timing is observed to increase when the connector is re-connected.
Fuel System:
1. The fuel pump has been proven to be providing adequate FLOW in addition to generating pressure. Remove the return line at the tank and force the fuel pump to run. Lots of liquid returning to the tank? Pressure does not equal flow!
2. The fuel pressure regulator is maintaining a pressure of around 12 PSI of fuel pressure
3. The injectors are verified as having the correct part number as those called for in your year and displacement of engine.
4. You have verified a solid, uninterrupted power supply to each injector
5. You have verified the operation of the fuel pump via the oil pressure switch on the back of the intake (3 PSI or greater = fuel pump runs)
6. You have verified the operation of the fuel pump relay on the firewall and that it is receiving and sending an un-interrupted supply of power to the fuel pump for extended periods of time (hot coil = reduced magnetism = power off to the fuel pump if the oil pressure switch has failed)
Controls:
1. Spark plug wires are routed so they will not electrically interfere with the unsheilded signal wiring in the control harness.
2. The ECM is reciving an un-interrupted battery supply voltage on pins B1 and C16.
3. The ECM is recieving an ignition controlled voltage supply on pin A6 whenever the key is in the ON or CRANK positions
4. The ECM is securely grounded to the engine block on pins A12 and D1
5. The ECM is securely grounded to the engine block and has a solid ground connection to the O2 sensor on pin D6
6. The ECM is properly connected to the ignition module via the white wire from pin D4 on the ECM to terminal D on the ignition module (grounding this wire with the ignition on should activate the fuel pump relay) as well as the white / purple wire from pin B5 on the ECM to terminal C on the ignition module. This wire carries the reference pulses from the pickup coil
7. The ECM is properly connected to the ESC module with a yellow / red wire from pin B7 on the ECM to terminal C on the module. This wire sends an ignition retard signal to the ECM when pinging is detected.
Other checks:
1. You have properly set minimum air on the throttle body (short the ALDL port with the ignition on to display codes for 45 seconds, disconnect the IAC, start the engine and set the idle to approx 450 rpm, shut down, reconnected the IAC and remove the battery cables for 5 minutes to re-set the ECM and clear the IAC codes)
2. Your engine has no vaccum leaks in the throttle body shafts, intake gaskets, vaccum booster or other vaccum accessories. It maintains 18 - 20 inHG of vaccum at idle.
3. The EGR valve is in good operating condition and is the correct part for your intake manifold (the wrong valve may fit your intake, but cause a massive internal vaccum leak)
4. Your engine is equipped with a proper TBI camshaft. Camshafts used for even a stock carb engine will not function properly with a TBI engine unless programmed for it.
5. Your engine is equipped with stock TBI heads. Any other heads will require re-programming. TBI is a speed density system that operates on a large number of assumptions of flow values carefully mesured on the stock engine.
6. Your engine is not suffering any mechanical issues (valve timing due to sloppy timing chain, incorrect valve lash, low compression, incorrect combination of engine parts etc)
7. You have verified the operation of all the engine sensors and actuators. Make sure you have believeable CTS, TPS and MAP sensor readings as compared to actual atmospheric readings taken by other instruments.
If all of this stuff checks out, then I am going to state that your ECM has failed. If you've replaced it already and kept your memcal, then I would suspect a problem with the memcal. If your ECM and memcal test out good on another TBI truck, along with your modules, distributors etc then your problem must be wiring. If your grounds and power supplies are good, then it must lie in the signal wiring.
TBI is simple, incredibly robust and reliable. If you set it up for success, you'll have a life time of solid operation out of it. But if you slap a TBI on an old carb engine, or swap to an aftermarket cam shaft that isn't designed to run with a TBI engine you will have endless problems with it. Speed density is a very simplistic injection platform that operates on a lot of assumptions about the engine. It has no way of measuring the actual flow of air or compression in the cylinders etc so all the fuel and timing requirements are inferred. This is why TBI does not like engine mods.
black dawg
1/2 ton status
If it were me, I would verify that it is losing injector pulse vs losing 12v to the injectors.
I had a tbi burb a few years ago that had very similar problems. it had lots of parts replaced before I got it. I tried several known good test parts on it, before I discovered that it was losing 12v to the injectors. There was a splice near the egr sol, and it had a bad spot it the wire just before the splice.
I had a tbi burb a few years ago that had very similar problems. it had lots of parts replaced before I got it. I tried several known good test parts on it, before I discovered that it was losing 12v to the injectors. There was a splice near the egr sol, and it had a bad spot it the wire just before the splice.
